It is known to provide vehicles suitable for driving in off-road conditions as well as on conventional roads including highways, such as four wheeled vehicles that are configured to drive all four wheels by means of a powertrain.
In certain situations such as when maneuvering at low speeds in off-road conditions, it is desirable to reduce a turning circle of a vehicle below that which the vehicle is otherwise capable of achieving. Vehicle turning circle can increase in certain off-road conditions due to understeer, which can be exacerbate on surfaces of relatively low surface coefficient of friction (‘surface mu’).
In one known vehicle, when a driver turns a steering wheel through greater than 270° to the left or right of a straight-ahead steering wheel position, full brake pressure is applied to an inside rear wheel in order to induce turning of the vehicle in the intended direction with a reduced turning circle.
It is also known to provide a control system for a motor vehicle for controlling one or more vehicle subsystems. U.S. Pat. No. 7,349,776 discloses a vehicle control system comprising a plurality of subsystem controllers including an engine management system, a transmission controller, a steering controller, a brakes controller and a suspension controller. The subsystem controllers are each operable in a plurality of subsystem function or configuration modes. The subsystem controllers are connected to a vehicle mode controller which controls the subsystem controllers to assume a required configuration mode so as to provide a number of driving modes for the vehicle. Each of the driving modes corresponds to a particular driving condition or set of driving conditions, and in each mode each of the sub-systems is set to the function mode most appropriate to those conditions. Such conditions are linked to types of terrain over which the vehicle may be driven such as grass/gravel/snow, mud and ruts, rock crawl, sand and a highway mode known as ‘special programs off’ (SPO). The vehicle mode controller may be referred to as a Terrain Response (TR) (RTM) System or controller. The driving modes may also be referred to as terrain modes, terrain response modes, or control modes.